This invention relates to a gate valve, and particularly to a gate valve having an improved actuator linkage between a manual handle and a slidable valve plate.
Gate valves having manual actuators are already known. My U.S. Pat. No. 5,445,190 issued on Aug. 29, 1995 shows a gate valve having an external actuator having a pivotal link connecting a rotary plate to a valve plate. Manual rotation of the rotary plate causes the link pivot connection to move toward or away from the valve flow passage, whereby the valve plate is moved between its open and closed positions.
The present invention is directed to a gate valve having an actuator that is simplified from the actuator shown in my U.S. Pat. No. 5,445,190. The present actuator comprises a direct pivotal connection between a manual crank and a slidable valve plate, such that the valve plate has a combined slidable and swingable motion as it moves between its open and closed positions.
U.S. Pat. No. 2,701,117 issued to N. Bashark shows a manual actuator for a gate valve that includes a manually-operated crank arm having a pin-slot connection with a slidable valve plate. One disadvantage of the pin-slot connection is that for a considerable portion of the crank arm stroke the pin exerts an oblique force on the valve plate, such that the plate can have a tendency to bind or wedge against the edge guides in the valve housing. A relatively large manual force is required to move the valve plate from its closed position. Premature wear on the sliding surfaces may be a problem.
U.S. Pat. No. 4,875,504, issued to W. Nicholson, shows an electric motor actuator attachable to a manually-operated gate valve to remotely operate the valve.
U.S. Pat. No. 5,439,198, issued to L. Reed, shows a gate valve actuator that includes a manual lever extending angularly away from the plane of the slidable valve plate. One disadvantage of such a lever actuator is that the valve is bulky and space-inefficient. The valve can only be used where a relatively large installation space is available.
The present invention is concerned with a gate valve having an improved low cost manual actuator. The actuator is designed to achieve smooth slidable motion of a slidable valve plate with a relatively small manual effort.
In the preferred practice of the invention, the slidable valve plate has a direct pivotal connection with a manually-operated crank arm. Manual rotation of the crank arm through a swing arc of about one hundred eighty degrees causes the valve plate to slide and at the same time to swing around its pivotal connection with the crank arm. The valve plate has a rocking action on edge guide surfaces formed in the valve housing, so that the valve plate moves freely between its open and closed positions. A relatively small manual effort is effective to operate the valve.
Further features of the invention will be apparent from the attached drawings and description of a preferred embodiment of the invention.